Coccydynia occurs when your coccyx, or the surrounding tissue, becomes damaged. This causes pain and discomfort at the base of your spine, particularly when sitting down.
The coccyx can be damaged in various ways, although in a third of cases it is not possible to identify a cause.
The various possible causes of coccydynia are outlined below.
Giving birth is thought to be the most common cause of coccydynia.
If you are pregnant, your coccyx will become more flexible towards the end of your third trimester (from week 27 to the birth). This is due to a release of hormones in your body which allow your coccyx, and the part of your spine above it, to bend and give way when you give birth.
But in some cases, childbirth can cause the muscles and ligaments (stretchy tissue that connects bones) around your coccyx to overstretch. This means these muscles and ligaments become permanently altered and can no longer hold your coccyx in the right position. This leads to coccydynia.
Injuring your coccyx
You can injure your coccyx if you suffer a hard impact to the base of your spine. For example, injury can sometimes occur during contact sports as a result of an accidental kick to the base of your spine.
Other ways that you can injure your coccyx include:
- falling over while skiing or ice-skating
- falling from high up, such as from a horse, and landing on your coccyx
- accidentally landing on one of the bars at the side of a trampoline
Although uncommon, injury to the coccyx has also been known to happen during sexual intercourse, particularly anal sex.
In most cases where the coccyx is injured, it will only be badly bruised. However, if your coccyx is severely injured, it may be partly dislocated (moved out of joint) or fractured (broken). If this happens, the bones that make up your coccyx may move around and cause pain, particularly when you are sitting.
Repetitive strain injury (RSI)
You may get coccydynia if you regularly take part in sports such as cycling or rowing. This is due to the motion of continually leaning forward and stretching the base of your spine.
If this motion is repeated many times, or if you hold a leaning forward position for a long period of time, the muscles and ligaments around your coccyx can become strained and stretched.
Straining your muscles and ligaments can permanently damage them. If this happens, your muscles will no longer be able to hold your coccyx in the correct position, and this will cause you pain and discomfort.
Read more about repetitive strain injury (RSI).
Sitting in an awkward position for a long period of time, such as at work or while driving, can put too much pressure on your coccyx. This causes pain and discomfort that will get worse the longer you stay in this position.
Read more information about how to sit correctly.
Being overweight or underweight
Being overweight or obese can place excess pressure on your coccyx when you are sitting down. This can cause coccydynia or make an existing case of coccydynia worse.
However, you may also develop coccydynia if you are very slim. If this is the case, you may not have enough buttock fat to prevent your coccyx from rubbing against the tissues surrounding it.
You can use the body mass index (BMI) calculator to find out whether you are a healthy weight for your height.
As we grow older the small discs of cartilage (a tough, flexible tissue) that help hold the coccyx in place can wear down. In addition the bones that make up the coccyx can become more tightly fused together. These can place more stress on the coccyx, leading to pain.
A less common cause of coccydynia is cancer. This can be cancer that first starts in the bone (sarcoma, which is an extremely rare type of cancer) or cancer that starts somewhere else in the body, such as the colon, and then spreads into the bone (metastatic cancer).